Salts of 3, 6 endoxohexahydrophthalic acid



ate; mono-n-.amylanimonium fmethylethyl n-i butylammonium 3,6 -endoxohexahydrophthalate;

mono n propylammonium monoisopropylammonium 3,6endoxohexahydrophthalate; ammonium monomethylammonium 3,6-endoxohexahydrophthalate; sodium diethylammonium 3,6-endoxohexahydrophthalate; potassium tri-n-amylammonium 3,6endoxohexahydrophthalate; lithium monoisobutylammonium 3,6-endoxohexahydrophthalate; bis(monoethanolammonium) 3,6- endoxohexahydrophthalate bis (diethanolammonium) 3,6-endoxohexahydrophthalate; bis(tri ethanolammonium) phthalate; bis monopropjanolammonium 3,6-endoxohexahydrophthalate; diethylammonium ethanolpropanolammonium 3,6 endoxohexahydrophthalate; sodium trietlianolammonium 3,6- endoxohexahydrophthalate; potassium monoethanolammonium v3,6endoxohexahydrophtllalate mono -tert-butylammonium monoethanolammonium 3,6-endoxohexahydrophthalate; bis- (ethylethanolammonium) 3,6-endoxohexahydrcphthalate; bis(npropyl-n butylethanolammonium) 3,6- endoxohexahydrophthalate; l bis-- (methyldiethanolammonium) 3,6-endoxohexahydrophthalate; ,monoethylammoniumethylisoamylethanolammonium Y3,6 endoxohexahydrophthalate; sodium isopropylethanolpropanolammonium 3,6-endoxohexahydrophthalate; potassium ethylethanolammoniurn 3,6-endoxohexahydrophthalate; dipropanolammoniumY ethylethanolammonium k3,6 .-.endoxohexahydrophthalate; andthe calcium, barium, strontium, magnesium, cobalt,zlnickel, zinc, cadmium, mercury, copper, iron,.and aluminum salts of 3,6-endoxohexahy-f drophthalicacid... :The invention wasconceived as an economicaland commercially feasible process for utilizing readily available chemicals and conventional equipmentto prepare excellent yields of the de'- sired salts in a satisfactory state of purity. "I'his goal. is achieved by sequentially-'following the steps indicated in the above equation, each step beingA conducted underfavorable Vconditions as will-be set forth herein. Y

fltisind'icated above that exo-cls-S-endoxo- 12,3,6-tetrahydrophthalic anhydride vis reacted with water to give exocis-3,6-endoxo-1,2,3,6 tetrahydrophthalic acid, and that this acid is then reacted-with base in- -Water solution to'give aneutral salt of said acid. The base may be an inorganic base,fan organic base, a mixed inorganic base, a mixed organic base, -or `a mixed inorganic-organic base. 'It is'of course understood that the base is capable of-forming lone ofthe types: of saltsdened above.

Therefore the treatment of the anhydride with water and subsequently with base is conducted in a temperature range which is conductive to maintaining the anhydride and acid in a stable condition, so that the desired salt formation can take place.

After the eXo-cis-3,6-endoxo-l,2,3,6tetrahy drophthalic acid has been converted to a watersoluble neutral salt of said acid, temperatures may be employed which are somewhat greater thanthose employed during conversion to the salt. It must not be inferred, however, that such salts are stable in all temperature ranges, for

such is not the case.

)Therefore it-is a feature of the invention that the hydrogenation of the Water-soluble neutral salts of 3,6-endoxo-1,2,3,6-tetrahydrophthalic acid be conducted in a temperature range which is conductive to maintaining said salts in a stable condition, so that they can react with hydrogen to form salts of the corresponding saturated acid,

i namely, 3,6-endoXo-hexahydrophthalic acid.

3,6 endoxohexaliydron.

hydrophthalic acid are markedly more stable than are the intermediates from which they are derived. It is not .known to what temperature levels they may be subjected without suffering decomposition, but for al1 practical purposes they may be regarded as stable.

' mitting economy and ease of operation; (c) is commercially available at a reasonable price, permitting still further economy; (d) does not rupture the endoxo linkage and thus give hydrogenated derivatives of phthalic acid. It has been discovered that nickel catalysts and cobalt catalysts meet these requirements particularly Well.

Many modifications -of nickel catalysts and cobalt catalysts are known to the art, and no extensive discussion of preparational methods is i1 needed.

AV particularly useful and well-known modification is the Raneytype rof catalyst. The general prccedure for preparing such a catalyst is to treat a vfinely vdivided nickel-aluminum alloy or cobaltaluminum alloy with aqueous caustic soda. This 1,2,3,6.-tetrahydrophthalic anhydride with water` -and subsequentlyiwith base, it is important to take recognition of the fact that `both this anhY- drideand the corresponding exo-cis-S-endoxo-i` temperatures be.v

1,2,3,6-tetrahydrophthalic acid are unstable.' at

operationM converts the aluminum into sodium aluminate, which is soluble, and renders the nickel (or cobalt) capable of adsorbing large quantities of hydrogen. e

'Another well-known modification is the nickelon-kieselguhr (or other porous support) type of catalyst; The. support is impregnated with a water-soluble'nickel salt, andthe resulting mass is treated with a reagent capable of precipitating .the nickel rin the form of its oxide, hydroxide, or

'I5 the ynoble metal catalysts have been used in effecting small-scale icatalytic ihydrogenations 4.Semevvthalnsimilar'i chemicallyfto those hydrogenae tions 'disclosed therein. Such .'catalysts,` however, areyery expensiye, and small losses that are 'likely to attend fcommercial operation :become .quite serious economically speaking. Moreover, .noble metal catalysts oftenv are subject to the vagaries CII of poisoning by traces of'impurities Which are i such that hydrogenation proceeds. very lsatisfactorily'ven :under `restricted .temperature conditions'. Moreover, theydo not readily lose their activity, such .as by `rmisoning for example, and thustheyfmay be used over long periods .of time.

The desired products, namely, Water-soluble neutral salts. of ,exocisffendoxohexahydrophthalic acid, 4are obtainedfinialmost quantitative yields.` Theyl are obtainableiin concentratedaqueous :solution merely by simple separation from the .-catalyS-t, ,for 4instance by decantation 4`and/or filtration. If Il for any reason the products are desired in .moreconcentrated form, vor :as dry, free-:flowing Apowders, this. .may be ,accomplished by evaporation of 4the :Concentrated aqueous solutions, for example.

, In a preferred procedureforYpracticing the yinvention, exo-cis-3,6endoxo 12,356 .-itetrahydrophthalic anhydride `is s lurriged `with water in a mixing` tank. Water, ice, .and :a stoichiometric proportionfof base to anhydride ,are `,mixed With the slurry. Addition of these materials is carried out in such a manner that theitemperature of the mixture `.iskept belowf75-C. and preferably below 40C..

The concentrated solutionfofWater-soluble neutral. salt of exo-cis-3,6endoxo1,2,3,6.tetrahy drophthalic acid so obtained is transferred by suitable. means, as. for example by pumping, to eduipment suitable ,for conducting catalytic hydrogenation under moderate pressure. Various typesofequipment may beused, butstirring autoclaves adapted tothe purpose have been found convenient. Such adaptation should of coursen- Qludesomeecient meansoi cooling.

kA suitable quantity of any one ofthe preferred catalysts .is now added to the autoclave. The ,latter isclosed, stirring'iscommenced, and hydrogen isfintroduced into the autoclave until the pressure therein is say approximately 300 p..s. i. g., theparticular pressure not being critical. Hydrogenation proceeds rapidly and exothermically, and additional hydrogen is introduced as needed tomaintain a pressure of say `the approximate orderofmagnitude already noted.

`fDuring said ,hydrogenatiom the temperatur of4 the reacting "mass lis preferably maintained below 100 C. and s till :more preferably beloW 50 C. The temperature should, of course, be high enough for hydrogenation to take place, andlpreferably is above C. and still more preferably .above C. 'Thus apreferred range is from .0 IC. to 100 C. 'and particularly from 15 \C. to 50 C. The Ytop permissible temperature in any casef'that atWhicha large degree ci` decomposition of ithe starting .salt Stakes iplaee. In the .case ,of .the inorganic .salts' Zsuch :as 'the disodium: salt, ,for example, temperatures .up v.to 125 C; imay. ibeiemployed, .whereas in .the leasev of. organic `salts such. as the amineisalts, or .mixed inorganiceorganic salts4 it -isibetter :not :to exceed 100 C. in View of danger of substantialdecomposition.

.Owing to the exothermic nature .of the :reati--v tion,.;it isV frequently Vnecessary '.to. cool the reaction mass. during iat least some stages of the reaction, in order to hold the mass .Within 'the prefer-redk temperature range..

Completioniof ythe reaction '.is indicated `when substantially .nomore hydrogen is .being .taken up .by 'the reaction mass, :as evidenced. by .a .confstant gaugefeading. ,Seyeral hours, .say up to armaximum .of vabout .or .6 hours, ,are .required to complete lthe reaction. AAt .this point it is advisable, .to insure :completeness .of reaction, to continue. .stirring `for a short time, .say ,about 1/2 hour `to 51 hour., .at :about the same pressi-.1re4 and temperature .as before.

vSltirring ,is then :discontinued .and .the ,pressure is released from .the autoclave. The system allowed to .stand :for J'about .1/2 .hour ,to ,permitathe catalyst ,tosettle out. The bulk of the .concentrated aqueous solution Loi the water-soluble neutral salt of Vexo cis-3,6 -endoxohexahydrophthalic acid `is removed-trom the `autoclave by any A.means which .doesnot .agitata `the solution, as iol .exemple :by means of .afdecanting well veine A small portion of ythe solution .is purposely not removed, in Order that the catalyst will :remain in vplace for the-next hydrosenatgon run.

.In actual lpractice .it .is d'icultfto remove. the aqueous solution from the autoclaue without carrying ,along a small amount of catalyst. For this reason it is advisable to Vadd@J small amount of ,fresh catalyst to the autoclave before proceeding with lthe next Bygoperating in this manner, the economy in use of catalyst is ,note- Worthy, as is demonstrated inione-Qfftheaexamgples given below.

The immediate product --as taken from the autoclave, need .only be :filtered to render it suitable for packaging, storing, and merchandising.

Or if desired, the 'immediate product "may 'be further processed.

Preferred 'temperatures for 'conducting v,the hydrogenation have `been indicatedr above. 'I'hey are temperatures at which vthe -Water-soluble neutral salts of exo-cis--endoxo-1,2,3;6tetraf hydrophthalic acid Aare substantially stable andv do vnot decompose. It should be pointed out that there is another `reason lfor conducting this step-of the `process under these Vrelatively mild temperature conditions. It `has been 4found that the endoxo linkage which Vis bridged between carbon atoms k3 and 6 of 'the fcarbocyclic ring isV stable at such temperatures. 4Should the endoxo linkage be ruptured, as might Aoccur -at substantially 'higher temperatures, it is obvious thatA undesirable side reactions would result. One such side reaction might Well be 'hydr0gen01jysis with attendant formation of derivatives of hexahydrophthalic acid.

The `following examples provide illustrations of the practice -of the invention in the Vpreparation'of water-#soluble neutral salts of 3,6-endoxohexahydrophthalic acid.

Eample 1 Fifty-seven pounds of water and z25 lpounds of exo cis "3,6 endoxo 1,`2,3,6 tetrahydrophthalic anhydride were mixed together in a 50 gallon mixing tank. To the resulting slurry were added 47 pounds of ice and 37.5 pounds of 32% caustic soda solution. The addition was carried out slowly and with continuous mixing. By so doing, the temperature was maintained between 30 C. and 40 C.

The resulting concentrated aqueous solution of disodium exo-cis-3,6endoxo-1,2,3,6-tetrahydrophthalate Was pumped to a 25 gallon stirring autoclave fitted suitably for conducting catalytic hydrogenation.

To the aqueous solution in the autoclave was added 320 g. of Raney nickel catalyst and the autoclave was then closed and agitation was commenced. Hydrogen was introduced to a pressure of 300 p. s. i. g. As the reaction proceeded, heat was evolved and the autoclave was sprayed with cool `water as needed. In this way the temperature was maintained between 30'o C. and 40 C. throughout the reaction period, the average temperature being 36 C. Also as the reaction proceeded, the hydrogen consumed by reaction 'was compensated for by introduction of additional hydrogen as needed. In this way the pressure within the autoclave was maintained between 200 p. s. i. g. and 300 p. s. i. g. throughout the reaction period. The reaction mass stopped taking up hydrogen after 31/4 hours, and agitation was continued for an additional 1/2 hour.

Agitation was then discontinued and the pressure was released from the autoclave. The system was allowed to stand for 1/2 hour, during which time the catalyst settled to the bottom. 141 pounds of the aqueous solution was removed from the autoclave by means of a decanting lwell pipe, and the solution Wasthen ltered. The remaining 25.5 pounds of solutionwas left in the autoclave together with the catalyst.

The iiltered solution, which was clear, had a light straw color. It was shown by analysis to contain 20.3% of disodium exocis-3,6endoxohexahydrophthalate.

Example 2 Starting with the autoclave left as at the end of Example 1, that is, containing 25.5 pounds of the aqueous solution of hydrogenated product and substantially all of the Raney nickel catalyst charged into it originally, a series of 45 additional runs was made.

In each run, the respective Weights of exo-cis- 3,6-endoxo1,2,3,6-tetrahydrophthalic anhydride, Water, ice, and 32% caustic soda solution were the same as those used in Example l.

f Over the series, small amounts of fresh Raney nickel catalyst were added as make-up. The aggregate amount of these additions was 1475 g., thus demonstrating economy of catalyst usage, particularly since most of the catalyst lost was removed mechanically with the product solution. Also over the series, other reaction conditions such as temperature, pressure, and time of reaction were maintained substantially the same as in Example 1.

At the end of each run except the last, the autoclave was partially discharged by the same decantation procedure used in Example 1. At the end of the last run, the autoclave was completely discharged by means of a Well pipe leading to the bottom. The individual solutions were ltered and composited.

In this series of 45 runs, 1125 pounds of exocis 3,6-endoxo-1,2,3,6-tetrahydrophthalic an- 8 vhydride was used. There was obtained 7414 pounds of clear, straw-colored ltrate containing 1502 pounds of disodium exo-cis-3,6endoxo hexahydrophthalate, as shown by analysis. This represents a yield of 96.5%, based on the anhydride.

Example 3 750 grams of exocis3,6endoxo1,2,3,6-tetra hydrophthalic anhydride and 1620 grams of water were intimately mixed to form a slurry. To this slurry 1500 grams of ice and 1080 grains of 33% caustic soda solution were slowly added, the mixture being stirred continuously during the addition. The mixture Was thus held at approximately room temperature.

The concentrated aqueous solution of disodium exo cis 3,6 endoxo 1,2,3,6 tetrahydrophthalate thus obtained was transferred to a 2- gallon stirring autoclave suitably tted for conducting catalytic hydrogenation.

37 grams of Raney cobalt catalyst was charged to the autoclave. The latter Was then closed, stirring was begun, and hydrogen was introduced to a pressure of 300' p. s. i. g. Hydrogenation took place and the temperature increased, but at no time during the reaction was the temperature inv excess of 31 C. The hydrogen consumed as the reaction proceeded Was compensated for by introduction of more hydrogen, and the pressure inside the autoclave was thus maintained between 250 p. s. i. g. and 300 p. s. i. g. throughout thev reaction period. After 61/2 hours the reaction was complete, as evidenced by the fact that no4 anhydride (637 g., 3.84 moles) was placed in a 5-liter, 3-neck iiask equipped with stirrer, thermometer, and dropping funnel. The ask was supported in an ice bath. Water (2000 cc.) was added to the flask, and a solution containing 506 g. of potassium hydroxide (7.68 moles) dissolved in 1000 cc. of water was slowly dropped in from the funnel. The temperature was maintained between 10 C. and 20 C.

There was thus provided an aqueous solution of dipotassium exo-cis-3,6endoxo-1,2,3,6tetrahydrophthalate, which was transferred to a 2- gallon hydrogenation autoclave. Raney nickel catalyst (200 g.) was placed in the autoclave. Hydrogenation was carried out at room temperature, the maximum temperature during the reaction being 27 C., and at a maximum pressure of 400 p. s. i. g. until no further drop in pressure was noted. This required about 1% hour.

The reaction mixture was taken from the autoclave and ltered twice to eiect separation of catalyst from the solution. There was thus obtained a 24.2% aqueous solution of dipotassium exo-cis3,6-endoxohexahydrophthalate.

Example 5 EXo-cis-3,6endoxo-1,2,3,6 tetrahydrophthalic anhydride (761 g., 4.58 moles) Was placed in a 5-liter, 3neck flask equipped with stirrer, thermometer, and dropping funnel. The iiask was, supported in an ice bath. Water (2683 cc.) wasv 'added toi the'r fl'ask, and`28 aqueous ammonia.

' wassloW-ly dropped in fror'n therurinel. 'I-hetemperaturemaintained between 110"y C. and `20`CL There wasV thus provided *an aqueousl solution of diammoniu-m' exo-cis-BLG 'en'doxol,ZBG-tetrahydrophthalate, which' was-transferred ftfoa 2- gallon hydrogenation autoclave. Raney nickel catalyst (-200- gr was placed in the autoclave. Hydrogenatiorr was carriedioutfat room temperature, the maximum temperature during the reaction being 25 C., and at a maximum pressure of 400 p. s. i. g. until no further drop in pressure was noted. This required about 1%, hour.

The reaction mixture was taken from the autoclave and lteredV twice to effect separation of catalyst from the solution. There was thus obtained a 25.2% aqueous solution of diammonium exo-cis-3,6-endoxohexahydrophthalate.

Ervample 6 Exo-cis-3 6-endoxo-1,2,3,6 tetrahydrophthalic anhydride (430 g., 2.59 moles) was placed in a 5-liter, 3-neck ask equipped with stirrer, thermometer, and dropping funnel. The flask was supported in an ice bath. Water (3047 cc.) was added to the ask, and triethylamine (523 g., 5.18 moles) was slowly dropped in from the funnel. The temperature was maintained between C. and 20 C.

There was thus provided an aqueous solution of bis(triethylammonium) exo-cis-3,6endoxo 1,2,3,6-tetrahydrophthalate, which was transferred to a 2-gallon hydrogenation autoclave. Raney nickel catalyst (200 g.) was placed in the autoclave. Hydrogenation was carried out at room temperature, the maximum temperature during the reaction being 23 C., and at a maximum pressure of 400 p. s. i. g. until no further drop in pressure was noted. This required about 3A hour.

The reaction mixture was taken from the autoclave and ltered twice to effect separation of catalyst from the solution. There was thus obtained a 25% aqueous solution of bis(triethylammonium exo cis 3,6 endoxohexahydrophthalate. When aportion of this solution was evaporated, the salt was obtained as a very viscous liquid.

A 29.2% aqueous solution of exo-cis-3,6endoxo-1,2,3,6-tetrahydrophthalic acid was prepared by dissolving exo-cis-3,6endoxo-1,2,3,6 tetrahydrophthalic anhydride in the requisite amount ofwwater. The solution, which weighed 1600 g. and contained 2.54 moles of exo-cis-3,6 endoxo-1,2,3,-tetrahydrophthalc acid was neutralized with 371 g. (5.08 moles) of diethylamine. During the neutralization, the mixture was externally cooled to maintain its temperature at 40 C. or less. The resulting solution was treated with an additional 25 g. of diethylamine to insure a pH of at least 9, and was then diluted with water to a total weight of 3900 g.

The solution of bis(diethylammonium) exo-cis- 3,6endoxo1,2,3,G-tetrahydrophthalate thus prepared was placed in a 2-gallon hydrogenation autoclave. Raney nickel (25 g.) was washed into the autoclave with 200 cc. of water. The resulting suspension was stirred and heated to 100 C. Hydrogen was then admitted to a pressure of 350 p. s. i. g. Hydrogenation occurred readily'and was substantially completed in 3A hour, at which FTio time 'the drop- -fn pressure had `virtually ceased.

`the" neutralizing baser 'insteadof diethylamine gave similar results.

Having more particularly described the invention, it is to be understood that this is by way of illustration and that modifications may be made within the scope of the claims without departing from the spirit of the invention. For example, it is to be understood that processing equipment of types other than those specifically mentioned may be used. During the hydrogenation it may l at times be found more convenient to operate at pressures either lower or higher than those specifically mentioned herein. In fact, for reaction purposes pressure is not critical, pressure being used to speed up the reaction. It is also possible to use an entirely new lot of catalyst for each hydrogenation run, although it is uneconomic to do so. It is likewise possible upon completion of hydrogenation to lter the entire reaction mass, recovering the catalyst and recharging it to the reactor for the next run if desired. If desired, dispersions or suspensions may be employed instead of solutions. These variations as well as other modifications will occur to those who are skilled in the art upon becoming familiar herewith.

Accordingly, it is intended that the patent shall cover by suitable expression in the claims the features of patentable novelty which reside in the invention.

I claim:

1. A method for the production of a watersoluble neutral salt of 3,6-endoxohexahydrophthalic acid, which comprises subjecting the corresponding water-soluble neutral salt of 3,6- endoxo-1,2,3,6-tetrahyrophthalic acid to hydrogen pressure at a temperature below 125 C. in the presence of a catalyst selected from the group consisting of nickel and cobalt hydrogenation catalysts, while maintaining temperature conditions below the point at which a large degree oi decomposition of said second-mentioned neutral salt takes place.

2. A method for the production of a watersoluble neutral salt of exo-cis-3,6endoxohexa hydrophthalic acid, which comprises subjecting the corresponding water-soluble neutral salt of exo-cis 3,6 endoxo 1,2,3,6-tetrahydrophthalic acid to hydrogen pressure at a temperature below C. in the presence of one of the group consisting of nickel hydrogenation catalyst and cobalt hydrogenation catalyst, and maintaining said reaction conditions for a time sufficient to cause hydrogenation of said second-mentioned neutral salt to take place to produce said rstmentioned neutral salt.

3. The method of claim 1 in which the rstand second-mentioned neutral salts are inorganic salts of the exo-cis isomers of the respective acids, and in which temperature conditions are maintained below C.

4. The method of claim 1 in which the firstand second-mentioned neutral salts are organic salts of the exo-cis isomers of the respective faoids and inwhich temperature conditions are maintained below 100 C. 5.'The method of claim 11n which the salts tained between approximately 0 C. and approx- .,imately 100 C.

6. -The method of claim 5 in which the respective salts are alkali metal salts.

1.- The method of claim 5 in which the respecwtive salts are disodium salts.

8. The method of claim 5 in which the respective salts are diammonium salts. y

- 9..'The method of claim 5 in which 4the respective salts are bis(alkylammonium) salts.

10. The method of claim 5 in which the respective salts are bis(diethy1ammonium) salts.

1l. The method of claim 5 in which the respective salts are bis(triethylammonium) salts.

12. The method of claim 5 in which the respective salts are bis-(triethanolammonium) salts.

JOHN F'. OLIN.

No references cited. 

1. A METHOD FOR THE PRODUCTION OF A WATERSOLUBLE NEUTRAL SALT OF 3,6-ENDOXOHEXAHYDROPHTHALIC ACID, WHICH COMPRISES SUBJECTING THE CORRESPONDING WATER-SOLUBLE NEUTRAL SALT OF 3,6ENDOXO-1,2,3,6-TETRAHYROPHTHALIC ACID TO HYDROGEN PRESSURE AT A TEMPERATURE BELOW 125* C. IN THE PRESENCE OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF NICKEL AND COBALT HYDROGENATION CATALYSTS, WHILE MAINTAINING TEMPERATURE CONDITIONS BELOW THE POINT AT WHICH A LARGE DEGREE OF DECOMPOSITION OF SAID SECOND-MENTIONED NEUTRAL SALT TAKES PLACE. 